The present invention relates to an abrasive layer divided into discrete blocks by a network of grooves, and more particularly, to an improvement in the making of grooves on the abrasive layer.
Various problems exist in the traditional application of plastic sheets evenly coated with abrasive particles as abrasive sheets in surface polishing, as abrasive dust accumulates between the abrasive sheet and the surface of the object, preventing the polishing process from going smoothly.
The traditional abrasive sheets are manufactured by evenly applied abrasive particles mixed with resin adhesive agent on the surface of plastic sheets. When used to polish the surface of metal and other objects, abrasive dust accumulates between the abrasive layer of the abrasive sheet and the surface of the object, preventing proper polishing, and moreover, abrasive particles drop out of the sheet and make scratches on the surface of the object. Finally, as the polishing proceeds, more and more abrasive dust and abrasive particles drop from the object being polished and the abrasive sheet, which dust and particles accumulate and stick to the edges of the object, causing the problem of round-shouldered polished surfaces instead of flat ones. It was, therefore, necessary to remove abrasive dust during the polishing process.
Meanwhile, with the recent use of magnetic heads in computer floppy discs for the input and output of information, a problem arises in that these magnetic heads attract dirt from the part of the floppy disc they contact when used over a long period. To remove the dirt from magnetic heads, an abrasive diskette for lapping and cleaning magnetic recording heads (IBM Technical Disclosure Bulletin, Vol. 20, No. 8, January 1978) was developed. However, problems still exist as the dirt removed in this way would later stick to the magnetic heads again.
For this purpose, there was also developed a cleaning tape for magnetic heads (U.S. Pat. No. 4,138,229) which employs an abrasive layer of particles of two different diameters to collect dirt between the bigger particles. This removes the dirt quite well, but the bigger particles are highly liable to scratch the magnetic heads in lapping; in addition, there is technical difficulty in manufacturing a dispersion of bigger particles evenly among smaller particles in the abrasive layer.
Also developed was mylar tape to which a dacron fabric is bonded by an adhesive layer. The dacron fabric projects and cleans off the dirt from the magnetic head by lapping it mechanically on the surface (U.S. Pat. No. 4,408,241).
But the dacron tape removes only the soft dirt while hard particles and magnetic crystalline powder in the dirt from the magnetic disc in the dirt remain intact.